Inconsistent syntax for NumericOnly grammar production

I noticed that gram.y has

NumericOnly:
FCONST { $$ = makeFloat($1); }
| '-' FCONST
{
$$ = makeFloat($2);
doNegateFloat($$);
}
| SignedIconst { $$ = makeInteger($1); }
;

but

SignedIconst: Iconst { $$ = $1; }
| '+' Iconst { $$ = + $2; }
| '-' Iconst { $$ = - $2; }
;

The inconsistency here means that you can do, for example,

regression=# set random_page_cost = +4;
SET
regression=# set random_page_cost = 4.2;
SET

but not

regression=# set random_page_cost = +4.2;
ERROR: syntax error at or near "4.2"
LINE 1: set random_page_cost = +4.2;
^

That's weird enough in itself, and the problem is about to get more
widespread because the partbound_datum production depends on NumericOnly.

Any objections to allowing "+ FCONST" here? I'm inclined to
fix this and back-patch it as well.

regards, tom lane